Silurian Rocks of the South of Ireland to those of North Devon. 141 
the Carboniferous Limestone and the Glengariff slates and grits. At Timoleague, 
and south of Bandon, the Kiltorean beds are in considerable force, but the main 
mass of the Old Red Sandstone is not represented. Similar conditions prevail in 
the district lying to the north-east and south of Cork, and I shall only refer to one 
other section, which has been very carefully measured by Mr. M‘Henry, of the 
Geological Survey, because it not only illustrates the nature of the hiatus but also 
shows that the Glengariff beds are highly unconformable to those which are in 
contact with them. ‘The section (Fig. 4) is taken along the side of Cork Harbour, 
between Monkstown and Passage :— 
Fig. 4.—Section through Monkstown and Passage, showing unconformity between the 
Glengariff and Kiltorcan Beds—Distance about 3 Miles. 
Monkstown. Passage. 
} i | TI WINN); Yj) GLC LYBAY; ee Lee 
Channel call ELT Ml MMMM REE SSS aoe 
: ) x SS SEQ 
YY) La Feri eek eae ere ese eee eae K WQS 
> vn Ss — 
L G L 
L.—-Carboniferous Limestone. S.—Carbons. Slate and Coomhola Beds. K.~—Kiltorcan Beds. G.—Glengariff Beds ; 
1. Upper Purple Slates, &c. ; 2. Purple ard Green Grits and Slates. yx ——Strata not seen. 
By an examination of this section it will be seen that the Kiltorcan beds and 
Carboniferous Slate rest, in the direction of Monkstown, on Glengariff beds which 
are much higher up than those upon which the same formation rests in the direction 
of Passage. The beds at Passage are, in fact, from 2,000 to 3,000 feet below those 
at Monkstown—the former consisting mainly of purple and green grits, the latter 
mainly of purple slates, forming the upper division of the Glengariff series. It is 
not often that it is possible to obtain so clear an evidence of unconformity, although 
the evidences of the hiatus are everywhere plain and satisfactory. The above cases 
will probably suffice to illustrate the relations of the older and newer formations 
of the county Cork and adjoining districts of Kerry and Waterford, pending the 
publication of the revised maps of the Geological Survey. 
IlI.—Paleo-Physical Geography. 
These peculiar relations to each other of the two groups of uncontormable 
strata are of interest as throwing light on the physical geography of the Palaeozoic 
rocks in this part of Ireland. There is only one way, as it seems to me, 1n which these 
relations can be explained. To suppose that all these breaks as they occur through- 
out several hundreds of linear miles (often well seen in road and river sections) can 
be explained by the presence of faults dislocating the strata is out of the question. 
It is seldom that there is any evidence of fracture, or local disturbance at the points 
of junction where visible. On the contrary, the change from the purple slates or 
grits of the Glengariff series to Carboniferous beds is generally abrupt, decisive, 
and without fracture. The explanation of the absence of the formations must, 
therefore, be that they were never deposited ; in other words, that there was an 
